Can sash windows be made energy-efficient?

Yes — modern replacement sashes use double or triple glazing with warm-edge spacers, draught-stripping, and insulating timber frames. Whole-window U-values from 1.3 W/m²K are achievable while keeping authentic appearance.

Do I need planning permission to replace sash windows?

Inside a Conservation Area or for Listed Buildings, yes — you'll need Listed Building Consent or sometimes planning permission. We handle the application drawings and specifications. For most non-listed homes, replacement falls under permitted development.

Are uPVC sash windows acceptable in conservation areas?

Sometimes — slim-profile heritage uPVC sashes with authentic glazing bars and horns are accepted in many (not all) conservation areas. We check with your local conservation officer before quoting.

How much do replacement sash windows cost?

Typical pricing: uPVC sash from £900-£1,400 per window installed; engineered timber sash from £1,400-£2,200; bespoke heritage timber for listed buildings £1,800-£3,200. We provide fixed-price quotes after survey.

Will the new sashes look authentic?

Yes — we match horn profiles (lamb's tongue, ovolo, etc.), glazing bar widths (usually 22-26mm), and paint colours. Side-by-side with originals, the only visible difference is the absence of putty lines on modern double-glazed units.

Sash Window Replacement UK | Heritage Timber & uPVC

Sliding sash windows are the architectural signature of British period properties — Georgian, Victorian, and Edwardian terraces, townhouses, and cottages. Original timber sashes often suffer from rot, draughts, rattle, and single-glazed inefficiency. S&K Glazing manufactures and installs replacement sash windows that match the original sightlines, glazing bar layouts, and sash horn profiles, but deliver modern U-values from 1.3 W/m²K and acoustic reductions up to 42dB. Available in engineered timber or slim-profile uPVC for conservation areas where uPVC has been approved.

Why choose our sash window replacement

Authentic sash window aesthetics — horns, beadings, glazing bars all matched to your original
Modern thermal performance — whole window U-value from 1.3 W/m²K (70% improvement over single glazing)
Optional acoustic specification — laminated glass reduces traffic and aircraft noise by 35-42dB
Spiral balance or traditional weight-and-pulley operation
Conservation-area and listed-building specifications available

Speak to our glazing team

Free survey, fixed-price quotes, no pressure sales. Call us, message on WhatsApp, or fill in the form — we typically respond within an hour during working days.